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What would be the easiest way in Ruby to pop a specific element from an array, similar to the .delete method of

a.delete(element)

rather than popping the first/last element or using .slice?

To make this more specific: for example, I can do

case names.sample when "John", "Dave", "Sam"
  a.delete(names.sample)
end

to delete one of those names from a when it appears as a sample from names

However, I intend to use multiple samples and using a.delete()will remove all elements at once, rather than in succession like the result produced from shuffle!.pop where elements are popped in succession, so that the name can no longer be selected as a sample from a after the same name has been selected as a name.sample

I was wondering what the easiest way would be in Ruby to pop off these elements in succession, or if it is even possible at all in this context.

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  • Not sure I understand what you're asking. You know that a .pop method exists in ruby? a.pop(index) Commented Nov 17, 2018 at 21:34
  • Sorry, I realize the wording may be confusing. I meant if there is a way to achieve the same result as using ` a.pop(element) ` which, from what I've researched, doesn't appear to be a thing unless used to dictate how many elements are popped. Whereas ` a.delete(element) ` can be used to run something like 'a.delete(name.sample)' as part of an "if" statement, if that makes any sense. Commented Nov 17, 2018 at 21:49
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    Possible duplicate of How can I delete one element from an array by value Commented Nov 17, 2018 at 21:52
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    I don't understand your question and I don't think I'm alone. It shouldn't be hard to word it so that it is complete and unambiguous, but if you are having trouble with that please at least include some examples. Be sure to show the expected or desired result for each example, and make sure all inputs and outputs are valid Ruby objects. More generally, when clarification of a question is requested please edit your answer rather than trying to elaborate in comments (which may not be seen by all readers). Commented Nov 17, 2018 at 22:44
  • Thanks for the advice. As you can probably tell I'm new to the website. I did edit and include clarification and examples in my original question after responding to the comment, so that should show up now. Commented Nov 17, 2018 at 23:06

2 Answers 2

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The Array class defines a pop method. It returns and deletes the last element in the array.

a = ["a", "b", "c"]
puts a.pop #=> "c"
puts a     #=> ["a", "b"]

You can optionally pass an argument to pop that specifies how many elements to pop off.

a = ["a", "b", "c"]
puts a.pop(2) #=> ["b", "c"]
puts a        #=> ["a"]

Addressing your last comment, you can use include?, index, and delete_at methods to achieve this. Assuming you're checking for "b" in an array:

a = ["a", "b", "c"]

value_index = a.index("b") #Returns the first occurring index of "b"
has_value = a.include?("b") #Returns whether "b" is in the list
a.delete_at(a.index("b")) if has_value #Removes "b" from the list

In this sample, "has_value" will be whether the a array contains the value "b", and "value_index" will be the first occurrence of "b". This will also delete the value "b" from the list.

If you want to remove all occurrences of "b", you can use include?, index, and delete_at with a while loop:

a = ["a", "b", "c", "a", "b", "c"]

while a.include?("b")
    a.delete_at(a.index("b"))
end
#a will now be ["a", "c", "a", "c"]

See also the documentation for Array.

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3 Comments

I'd write the last one as a.count("b").times { a.delete_at(a.index("b")) }. Or check here for nicer solutions with benchmarks.
That way works too, there's more than one way to do almost anything.
while a.include?("b"); a.delete_at(a.index("b")); end is just an elaborate way of doing a.delete("b")
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[..] intend to use multiple samples and using a.delete() will remove all elements at once, rather than in succession like the result produced from shuffle!.pop where elements are popped in succession, so that the name can no longer be selected as a sample from a after the same name has been selected as a name.sample[..]

Maybe you are looking something like this?

names = ["John", "Dave", "Sam"]

names.size.times { p names.delete(names.sample) }

#=> "Sam"
#=> "John"
#=> "Dave"
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1 Comment

Thank you, this was effective.

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